The present invention relates to a programmable controller having a processing unit, a display screen, an operator unit and signal inputs and signal outputs, where the processing unit, the display screen, the operator unit, the signal inputs and signal outputs are accommodated in a common housing, and where switching functions can be programmed by the user on the basis of predetermined functions by using a menu-assisted user interface on the display screen.
Such controllers have been programmed in a STOP state (application program not active) of the controller using a control panel integrated into the controller, with graphical monitoring of a screen likewise integrated into the controller. Further, the application program can be examined via the screen of the controller in the STOP state, and signal states of inputs and outputs of the controller are graphically presented in the RUN state (application program active).
An object of the present invention is to devise such a programmable controller, which markedly increases the capacity of the controller while maintaining the same level of operator convenience or programming convenience.
The present invention provides a programmable controller having a processing unit, a screen (14), a control panel (8), and having signal inputs (4) and signal outputs (6), the processing unit, the screen (14), the control panel (8), the signal inputs (4) and signal outputs (6) being accommodated in a common housing (2), and switching functions being programmable by the user via a menu-driven user interface on the screen (14). The status display is capable of being switched between an active display status, in which signal states of inputs and outputs of the controller, as well as signal states of function blocks and the like are displayed on the screen, and an inactive display status, in which no instantaneous display of signal states is presented on the screen.
According to the present invention, the processor running time or the cycle time of an executing (active) application program can be influenced in that the status display of the screen is capable of being switched between an active display status, in which signal states of inputs and outputs of the controller, and signal states of function blocks and the like, are displayed on the screen, and an inactive display status, in which no current display of signal states is presented on the screen. In standard mode, the status display on the screen is active. For this purpose, the signal states to be displayed must be interrogated at regular intervals during the execution of the application program and resupplied to the display (refresh). This refresh, however, requires valuable cycle time. In accordance with the present invention, the controller design makes it possible to turn off the screen""s status display, so that there is no refresh at regular intervals, and the cycle time is correspondingly reduced. In this way, processes that are even more time-critical can advantageously be managed.
In a specific embodiment of the present invention, a combination of at least two keys causes the status of the display status to be switched. Thus the status display is switched by preferably mutual actuation of two defined keys. In another specific embodiment of the present invention, this switching is implemented automatically, for example by the status display being activated only in every n-th cycle. If the average cycle time is 5-10 ms and a characteristic time relating to the perceptual capacity of the human eye is approximately 200 ms, it is desirable to activate the status display only in every twentieth to fortieth cycle, and thus to achieve a reduction of the cycle time.